Seatbelt Warning Light Cabling

Anybody knows of where the seatbelt LH Driver Side lock cable is connecting to? There are 2 pins: Black is Ground and Yellow is the signal. When the seatbelt clamp locks in, the lock shortens the Ground to the Yellow wire. My seatbelt warning light goes off when the engine starts up regardless the seatbelt is fasten or unclipped.

This 2-wire harness goes into the major harness at the end of the tunnel and I was not able to trace it in the tunnel under AC Control panel and other buttons or at the front end of the tunned with the cable tracer device.
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Yes, I've checked the seatbelt switch and it's working as you described: it shortens the black Ground wire to the Yellow-Blue (GL) and when clipping the belt in, it opens up.

I traced the Yellow-Blue wire to the front end of the Tunnel and it's coming to the Pin #1 of the Dashboard Connector A. The Yellow-Blue wire goes out from the other end of the connector and goes into the wire harness. I was not able to trace it further. On the Instrument Cluster connectors there is no any Yellow-Blue wire and there is no same wire on the Electrical Board connectors

You was right, the Yellow-Green (GV) coming out of Electrical Board connector "E" on the Pin #8 and it goes to the Pin#15 connecor "E" on the Instrument Cluster supplying +12V to the Seatbelt Warning Light, Shock Absurbers Light, and the Airbag Light. This wire also goes to the Pin #2 of the Dashboard Connector A.

The Ground signal is being supplied to the Instrument Cluster connector "E" on Pin #8, Pink-Yellow (SG) wire. This wire is not present on neither Dashboard Connectors A or B at the front end of the Tunnel. I noticed on the Instrument Cluster Connector "E" this Pin also shares Ground with other Pins when the Ignition Key is in the positin OFF, although on the Instrument cluster it is designated for a Ground for the Seatbelt Warning.

I followed your logic and shortened the Yellow-Blue from the Seatbelt lock to the Ground of the Seatbelt Warning light. When I did so, the Airbag and Battery Warning lighghts came on. Clipping the belt was switching all these 3 lights ON/OFF. When finished with this exersize, the Airbag Light is always ON now.

So:

1) Anybody knows of where the Yellow-Blue (GL) wire is going from the Pin #1 of the Dashboard Connector A?

2) Where the Pink-Yellow (SG) wire does go off the Pin #8 of the Instrument Cluster Connector E?

3) How to reset the Airbag light besides going to the dealership (had done so last Summer once aleady).

Note: in the Workshop Manual Vol. 3, pp H40-41 there is a procedure of resetting the light by shortening the Pin #1 of the diagnostic connector to the Ground for 5-10sec. My diagnostic connector doesn't have a Pin #1 but #2 and 3 only (the pins are marked on the connector).
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Just came from a local Ferrari shop who reset my airbag light. I asked the shop owner if he is aware if this feature could be re-programmed in the ECU by a prev. owner. He said he is not aware the Seatbelt Warning lights could be programmed. There was another 355 in the shop so the shop owner showed the Seatbelt Warning Light in another 355 behaved exactly the same: Comes up with ignition ON and goes off then, regardless if the belt is fasten or unclipped. He said it could be this way on ALL 355s, at least the US version.

Answering other questions: the instrument cluster screws not touching anything, all clear.

Yes, there is "0" Ohms b/w Pin #8 of the Instrument Cluster Connector E and Pin #1 of Dashboard Connector A.

On your diagram if there is a device that supplies ground to the bulb, at least for the EU version I would say now, it will be between the Pin #1 of the Dashboard Connector A and the Pin #8 of the Ground for the Seatbelt Warning Light.

Clarification: what triggered the AIRBAG light to go off was not having one of the connectors disconnected but I had plugged a shortcut wire to the back of the Pin #8 of the Instrument Cluster Connector E and the Pin #1 Dashboard Connector A - supplied the Ground from the seatbelt lock to the Seatbelt bulb. What I said because there is a device that manages the Ground for Seatbelt Warning, AIRBAG, SLOW DOWN light, and I think the Battery light (don't remember exactly but it were 3 warning lights that were going on and off when had the shortcut wire on and clipping the driver seatbelt on and off. I think what happened the AIRBAG ECU detected the AIRBAG light up when it was not supposed to be and threw an error code out which lit the AIRBAG light up then.

 

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Ok, the new wire tracer did the magic. I traced the Yellow-Blue (GL) wire coming from the Dashboard Connector A Pin #1 to the 137667 RELAY/SEAT BUZZ Pin #1. And here we see our Pink-Yellow (SG) Ground on the Pin #4 from the Seatbelt Warning light from the Instrument cluster (do these wires look BEAUTIFUL? )

So this is the device that's doing all the magic

I opened it up and found the speaker's base is a bare metal that could touch the resistors that surround it causing whatever issues and secured it with the fabrique-based electrical tape- similar one to the wire haness factory wrapping tape. Put everything back together and... TA-DA! Everything started to work!!


Here is how it works:

- A car key is in the lock and if the driver door is open: the buzzer goes off until you get the driver door OR remove the car key from the lock
- The driver door is closed and you start the engine with the driver seat belt UNCLIPPED: the Seatbelt Warning Light comes on then goes out at the same time with the buzzer
- The driver door is closed and you start the engine with the driver seat belt FASTEN: the Seatbelt Warning Light comes on and goes out with NO buzzer


Resume: I like this new tracer device. MUCH better than the original one which also was a bit more expensive I had bought at first.
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Hey Ian!

Without YOUR help I wouldn't do it!!

The diagram looks great! And you could take off the red question marks from where the Ground is supplied by the black wire to the seatbelt lock switch. It's a direct Ground regardless of any car key lock position, battery off switch or etc.

Not sure as I had mentioned at some time before that there is a difference in wiring b/w the US and EU cars, at least for the 355. I only noticed the difference in the temp control labeling in F vs. C and the coolant temp accordingly and the oil pressure for my car is in the lbs/sq. inch measuring vs. in atm. for EU.

DO NOT get that Gardner Bender ET64220, that's the very one I had bought at first and like you I had chose it at first because it's "branded" and etc. and found it completely useless and the main thing I noticed its' tracing signal is very weak pretty much so I was lucky I was able return it to the seller right away with a 20% restocking fee.

The one I got then is a JHK-XQ350. Not sure who is the manufacturer but appearing it's made in China. I got it off eBay for $27.99 USD vs ET64220 is for $45 USD or about in the US.

Telephone Phone Network Cable Wire Tracker Toner Tracer Tester with Carry Bag | eBay
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